The present invention relates generally to a valve having at least one electronic air/fuel ratio control module, and more particularly to control valve module for air/fuel ratio control for gaseous-fueled engines operating with a near-stoichiometric air/fuel ratio.
Trim valves are used in many industrial and commercial settings for a variety of applications. One application is the control of gaseous fuel flow to the combustion system of a gaseous fueled engine to maintain a desired air/fuel ratio. Examples of gaseous fuels are propane and natural gas. The combustion occurs in the engine cylinders. The air-fuel mixture is supplied to the cylinders from the engine intake manifold. For each cylinder head, an intake valve in the cylinder head opens to admit the air-fuel mixture from the intake manifold into each cylinder. After combustion, an exhaust valve in each cylinder head opens to allow the gaseous combustion products to flow to the exhaust manifold. The combustion gases may either be vented to the atmosphere or be ducted to a turbocharger, which derives energy from the hot exhaust gases to compress the air used by the engine.
The overall performance of the engine in terms of combustion efficiency, speed control, exhaust emission of pollutants and others, greatly depends on controlling the mixing of the air and fuel into an appropriate ratio for combustion and on regulating the flow of this mixture into the combustion part of the engine. Precise and reliable control of the combustion is very important for the efficiency and the safety of the combustion process, as is well understood by those skilled in the art. For example, it is well known that combusting a fuel with excess oxidant yields higher nitrogen oxides (NOx) emission rates. Combustion of a fuel with an uncontrolled excess amount of air can also lead to excessive fuel consumption and increase the production cost of the final product. On the other hand, incomplete combustion of a fuel generates carbon monoxide (CO).
NOx, CO and hydrocarbon (HC) emissions are regulated by the government to increasingly lower levels and in an ever increasing number of industries. In addition to the NOx, CO and HC emissions, many designs must meet the requirements of regulatory agencies that have adopted the standards published by governments, insurers, and industry organizations (such as UL, CSA, FMRC, etc.).
Catalysts have been developed to reduce, and in some applications, eliminate, the emissions. A catalyst that simultaneously eliminates HC, CO, and NOx is referred to as a xe2x80x9cthree-wayxe2x80x9d catalyst. The use of a three-way catalyst will reduce the emissions of a stoichiometric engine. However, for these emission reductions to be reliable and maximized, and to protect the catalyst element from premature aging or damage, a very precisely controlled air/fuel ratio is required.
The invention provides a control valve module for gaseous fuels on spark ignited reciprocating engines. The control valve module has a valve that controls gaseous fuel flow to a mixer or other device for air/fuel ratio control, an actuator for moving the valve position, and a controller. The controller receives a signal from a heated exhaust gas oxygen (HEGO) sensor that is an indication of the fuel/air ratio and actuates the valve to control the combustion mixture to a precise stoichiometric ratio.
The control valve module includes an interface for a user to configure parameters for one or two types of fuel. The user may select the fuel type, position dither amplitude and period, feedback strategy, and other control parameters.